In order to fit a bicycle to a particular rider, various parts of the bicycle must be moved with respect to the bicycle frame. Specifically, the seat and handlebars of the bicycle must be adjusted to position the rider on the bicycle where the seat, peddles and handlebar are all comfortably positioned with regard to the rider.
In order to adjust a handlebar stem with regard to the bicycle frame, often times various components of the neck assembly holding the handlebar stem on the bicycle frame must be disengaged and/or repositioned in order to locate the stem at the desired location for a particular rider. In most bicycle construction, the neck assembly is formed of a steel tube, extending upwardly from a front bicycle fork that is inserted through and rotatably retained within a head tube on the bicycle frame. The handlebar stem is positioned above the head tube and held on the tube by a pair of spacers located on the stem tube on the tube above the stem and between the head tube and the handlebar stem. Based on the construction of the majority of these prior art neck assemblies, the repositioning of the components of the assemblies to adjust the handlebar stem often requires that one or both of the spacers attached to the steer tube on opposite sides of the bicycle stem must be removed and replaced with spacers having a different size, and/or that the steer tube on the bicycle frame must be cut to the necessary length.
In either case, the time and materials required to reposition the handlebar stem on the steer tube for the bicycle frame are very significant. Further, if an individual or shop does not have the spacers of the necessary size or thickness, or cannot cut the steer tube to the desired length, it is not possible to reposition the handlebar stem where desired. Also, in those situations where the tube is cut, it will not be possible to readjust the stem back to the previous location as that part of the tube has been permanently removed.
Therefore, it is desirable to provide a handlebar stem adjustment assembly which allows for quick and easy repositioning of a handlebar stem on a steer tube without having to replace any components of the assembly or having to alter the structure of the bicycle frame. Further, the stem height adjustment assembly should have a strong and durable construction capable of withstanding the forces applied to the mechanism by the relative movement of the handlebar stem and the steer tube during normal operation of the bicycle.